Herbicides in Camps Bay (Cape Town, South Africa), supplemented

Abstract

During 2017 the herbicides alachlor, atrazine, butachlor, metolachlor, and simazine were detected in water samples, beach sediments and marine biota collected at Camps Bay, Cape Town, South Africa. During that period, the annual rain catchment record was 77,000 m3, whereas the volume of chemically laden sewage discharged via the marine outfall was 693,500 m3 making the marine sewage outfall by far the most predominant source for these herbicides in the bay. The chemical load in the discharged sewage was not removed by the applied pre-treatment step, which only uses a 3mm screen to eliminate plastic, paper, rags and other foreign materials. After passing through the Camps Bay pump station, the sewage is released to the bay at the following GPS position 33°56'42.214″ S 18°21'59.257″ E (Colenbrander et al., 2021) and at a discharge depth of 23m and 1497m from the beach. In our study the presence in marine biota of atrazine and simazine were taken as being indicative of the chemical signature of the sewage being released through the outfall, since these compounds were detected previously in the sewage prior to discharge. To our knowledge, our studies of the herbicides in diverse benthic organisms found in the near shore environment of Camps Bay are the first of their kind for this Western Cape region.